A rupture disk is used to release pressure from a pressurized system in response to a potentially dangerous overpressure situation. Generally, a rupture disk has a flange that is sealed between a pair of support members, or safety heads, forming a pressure relief assembly. The pressure relief assembly may then be clamped or otherwise sealingly disposed between a pair of conventional pipe flanges or between a pair of threaded fittings in the pressurized system. A first pipe conducts pressurized fluid to one side of the pressure relief assembly and a second pipe provides an outlet to a safety reservoir or may be open to the environment. The support members include central openings that expose a portion of the rupture disk to the pressurized fluid in the system. The exposed portion of the rupture disk will rupture when the pressure of the fluid reaches a predetermined differential pressure between the inlet and outlet sides. The ruptured disk creates a vent path that allows fluid to escape through the outlet to reduce the pressure in the system.
A rupture disk typically has a dome-shaped, rounded-shaped, or other generally curved rupturable portion and can be either forward-acting or reverse-acting. A forward-acting rupture disk is positioned with the concave side of the rupturable portion exposed to the pressurized system, placing the disk under tension. Thus, when an over-pressure condition is reached—i.e., when the system pressure exceeds a safe or desirable level—the rupture disk may release pressure by bursting outward. Conversely, a reverse-acting rupture disk (also known as a reverse buckling rupture disk) is positioned with its convex side exposed to the pressurized system, placing the material of the disk under compression. Thus, when an over-pressure condition is reached, the rupture disk may buckle and reverse—i.e., invert—and tear away to vent pressurized fluid.
The rupture disk industry has historically manufactured dome-shaped, rounded-shaped, or other generally curved rupture disks by moving rupture disk material from work station to work station for sequential processing steps, either manually, by robotic arm, or by a combination of the two.
A reverse buckling rupture disk may rupture by itself upon reversal. Alternatively, additional features may be provided to facilitate rupture. For example, a cutting structure or stress concentration point may contact the reverse buckling rupture disk on reversal, ensuring that rupture occurs. Exemplary cutting structures include one or more blades (e.g., a four-part blade like that provided by BS&B Safety Systems as part of the commercially available RB-90™ reverse buckling disk, or a tri-shaped three-part blade like that provided by BS&B Safety Systems as part of the commercially available DKB VAC-SAF™ rupture disk) and circular toothed rings (e.g., like that provided by BS&B Safety Systems as part of the commercially available JRS™ rupture disk). Other exemplary cutting structures may be positioned along the periphery of a rupturable portion. Still other exemplary cutting structures may be positioned in an X-shape, Y-shape, or irregular Y-shape designed to engage with the rupturable portion upon reversal.
Rupture disk assemblies using cutting structures are described in co-owned U.S. Pat. Nos. 4,236,648 and 5,082,133, the contents of which are hereby expressly incorporated by reference in their entirety. Exemplary stress concentration points are described in co-owned U.S. Pat. No. 5,934,308, the contents of which are hereby expressly incorporated by reference in their entirety.
The predetermined pressure differential at which a rupture disk will rupture is known as the “burst pressure.” The burst pressure for which a rupture disk is rated is known as the “nominal burst pressure.” The burst pressure may be set by way of the rupture disk's physical parameters, such as material thickness and dome height (also known as “crown height”). The burst pressure also may be set using various physical features, such as indentations. A rupture disk having an indentation—and methods of manufacturing such rupture disks—is disclosed, for example, in co-owned U.S. Pat. Nos. 6,178,983, 6,321,582, 6,446,653, and 6,494,074, the contents of which are hereby incorporated by reference in their entirety.
In general, the burst pressure of a known rupture disk for a given nominal burst pressure can vary as a function of the applied temperature. For simple tension-loaded (e.g., forward-acting) rupture disks, the variation in burst pressure closely correlates with the variation in tensile strength associated with temperature changes of a given rupture disk material. For reverse-buckling rupture disks, the variation in burst pressure with temperature is diminished, because material tensile strength is only one parameter influencing the burst response of such structures. Because the temperature of a pressurized system may vary, a rupture disk with reduced temperature sensitivity is desirable.
Physical features, such as score lines and shear lines (and other areas of weakness, also known as lines of weakness), may be used to facilitate opening of a rupture disk and control the opening pattern of a rupture disk. In a reverse buckling disk, for example, the disk will tear along a score line when the disk is reversing. Selected portions of the disk are usually left unscored, acting as a hinge area, to prevent the disk from fragmenting upon bursting and the fragments from the disk escaping along with fluid from the pressurized system.
Fragmentation of a rupture disk is also controlled through use of a transition area. The transition area appears between a rupture disk's dome and flange portions. The rupture disk industry has focused on using a transition area with a fixed radius to assist with fragmentation control. It is generally accepted that a radius that exceeds the thickness of the disk material is the best approach to controlling rupture disk fragmentation. Typically, for a rupture disk with a higher burst pressure, both the thickness of the disk and the radius of the transition area will be increased to control rupture disk fragmentation.
Some applications require a small rupture disk that is effectively “miniaturized”—e.g., with a diameter of about one inch or smaller. Typically, the physical features describe above—such as dome height, indentations, areas of weakness, and transition areas—are used to control the burst and fragmentation of miniaturized rupture disks as well as larger-diameter rupture disks. Reliance on such parameters and features limits the range of burst pressures that can be provided in a miniaturized rupture disk, however, and may result in unreliable variation in burst pressure or the inability to produce a desired burst pressure from available stock thickness raw material.
In addition, scored miniaturized reverse buckling disks suffer drawbacks arising from the need to push an excess of dome material through a small aperture upon reversal. Thicker miniaturized reverse buckling disks particularly suffer from this problem.
In light of the foregoing, there is a need for a miniaturized rupture disk that can be configured to meet a number of different burst pressure requirements, and can provide more reliable bursting performance. The rupture disk—and associated systems and methods—of the present disclosure achieves these, or other, advantages.